The Institute for Sustainable Infrastructure awarded Envision Silver to the Dixon Wastewater Treatment Facility, in Dixon, CA. The City of Dixon’s Wastewater Treatment Facility Improvements project is the culmination of years of collaboration between the city, Stantec Consulting, the state of California environmental regulators, and the public.
Improvements to the facility address a range of community needs – upgrading the aging plant itself, meeting increased capacity demands, addressing salinity limits placed on the facility by the state, etc.
The improvement project replaces the facility’s large 130-acre treatment ponds with an oxidation ditch design that has a significantly smaller exposed surface area, which reduces evaporative water losses a hundredfold. The retained water serves to keep the dissolved wastewater salts diluted, which reduces the effluent salinity. By solving the salinity issues through reducing evaporation and the activated sludge process, the wastewater treatment facility avoids more conventional salt-removal treatment methods that are costly, consume a lot of energy, and produce a hazardous brine waste.
Project planners also chose the oxidation ditch design because it easily accommodates new features, such as solar power and the use of recycled water at the plant or in the community. The design also incorporates robust nitrogen removal in the process as a saver of energy and costs long-term, and it proactively addresses groundwater nitrate contamination, which is considered the biggest long-term threat to groundwater drinking quality in agriculturally dominated areas worldwide, including the Central Valley of California.
Before approval of the project, the project team launched a public outreach program to inform and educate the public on the project plans, including incentives to remove salt-discharging water softeners, the benefits of the selected treatment technology, and any monetary implications. This outreach program helped address concerns and ultimately led to public and state regulatory approval of the facility improvements project.
The ISI Envision rating system measures sustainable infrastructure projects in five categories: quality of life, leadership, natural world, resource allocation, and climate and risk. Learn more about Envision and ISI at sustainableinfrastructure.org.